1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_SCHED_TASK_H 3 #define _LINUX_SCHED_TASK_H 4 5 /* 6 * Interface between the scheduler and various task lifetime (fork()/exit()) 7 * functionality: 8 */ 9 10 #include <linux/sched.h> 11 #include <linux/uaccess.h> 12 13 struct task_struct; 14 struct rusage; 15 union thread_union; 16 struct css_set; 17 18 /* All the bits taken by the old clone syscall. */ 19 #define CLONE_LEGACY_FLAGS 0xffffffffULL 20 21 struct kernel_clone_args { 22 u64 flags; 23 int __user *pidfd; 24 int __user *child_tid; 25 int __user *parent_tid; 26 const char *name; 27 int exit_signal; 28 u32 kthread:1; 29 u32 io_thread:1; 30 u32 user_worker:1; 31 u32 no_files:1; 32 unsigned long stack; 33 unsigned long stack_size; 34 unsigned long tls; 35 pid_t *set_tid; 36 /* Number of elements in *set_tid */ 37 size_t set_tid_size; 38 int cgroup; 39 int idle; 40 int (*fn)(void *); 41 void *fn_arg; 42 struct cgroup *cgrp; 43 struct css_set *cset; 44 }; 45 46 /* 47 * This serializes "schedule()" and also protects 48 * the run-queue from deletions/modifications (but 49 * _adding_ to the beginning of the run-queue has 50 * a separate lock). 51 */ 52 extern rwlock_t tasklist_lock; 53 extern spinlock_t mmlist_lock; 54 55 extern union thread_union init_thread_union; 56 extern struct task_struct init_task; 57 58 extern int lockdep_tasklist_lock_is_held(void); 59 60 extern asmlinkage void schedule_tail(struct task_struct *prev); 61 extern void init_idle(struct task_struct *idle, int cpu); 62 63 extern int sched_fork(unsigned long clone_flags, struct task_struct *p); 64 extern void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs); 65 extern void sched_post_fork(struct task_struct *p); 66 extern void sched_dead(struct task_struct *p); 67 68 void __noreturn do_task_dead(void); 69 void __noreturn make_task_dead(int signr); 70 71 extern void mm_cache_init(void); 72 extern void proc_caches_init(void); 73 74 extern void fork_init(void); 75 76 extern void release_task(struct task_struct * p); 77 78 extern int copy_thread(struct task_struct *, const struct kernel_clone_args *); 79 80 extern void flush_thread(void); 81 82 #ifdef CONFIG_HAVE_EXIT_THREAD 83 extern void exit_thread(struct task_struct *tsk); 84 #else 85 static inline void exit_thread(struct task_struct *tsk) 86 { 87 } 88 #endif 89 extern __noreturn void do_group_exit(int); 90 91 extern void exit_files(struct task_struct *); 92 extern void exit_itimers(struct task_struct *); 93 94 extern pid_t kernel_clone(struct kernel_clone_args *kargs); 95 struct task_struct *copy_process(struct pid *pid, int trace, int node, 96 struct kernel_clone_args *args); 97 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node); 98 struct task_struct *fork_idle(int); 99 extern pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name, 100 unsigned long flags); 101 extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags); 102 extern long kernel_wait4(pid_t, int __user *, int, struct rusage *); 103 int kernel_wait(pid_t pid, int *stat); 104 105 extern void free_task(struct task_struct *tsk); 106 107 /* sched_exec is called by processes performing an exec */ 108 #ifdef CONFIG_SMP 109 extern void sched_exec(void); 110 #else 111 #define sched_exec() {} 112 #endif 113 114 static inline struct task_struct *get_task_struct(struct task_struct *t) 115 { 116 refcount_inc(&t->usage); 117 return t; 118 } 119 120 extern void __put_task_struct(struct task_struct *t); 121 extern void __put_task_struct_rcu_cb(struct rcu_head *rhp); 122 123 static inline void put_task_struct(struct task_struct *t) 124 { 125 if (!refcount_dec_and_test(&t->usage)) 126 return; 127 128 /* 129 * In !RT, it is always safe to call __put_task_struct(). 130 * Under RT, we can only call it in preemptible context. 131 */ 132 if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) { 133 static DEFINE_WAIT_OVERRIDE_MAP(put_task_map, LD_WAIT_SLEEP); 134 135 lock_map_acquire_try(&put_task_map); 136 __put_task_struct(t); 137 lock_map_release(&put_task_map); 138 return; 139 } 140 141 /* 142 * under PREEMPT_RT, we can't call put_task_struct 143 * in atomic context because it will indirectly 144 * acquire sleeping locks. 145 * 146 * call_rcu() will schedule delayed_put_task_struct_rcu() 147 * to be called in process context. 148 * 149 * __put_task_struct() is called when 150 * refcount_dec_and_test(&t->usage) succeeds. 151 * 152 * This means that it can't "conflict" with 153 * put_task_struct_rcu_user() which abuses ->rcu the same 154 * way; rcu_users has a reference so task->usage can't be 155 * zero after rcu_users 1 -> 0 transition. 156 * 157 * delayed_free_task() also uses ->rcu, but it is only called 158 * when it fails to fork a process. Therefore, there is no 159 * way it can conflict with put_task_struct(). 160 */ 161 call_rcu(&t->rcu, __put_task_struct_rcu_cb); 162 } 163 164 DEFINE_FREE(put_task, struct task_struct *, if (_T) put_task_struct(_T)) 165 166 static inline void put_task_struct_many(struct task_struct *t, int nr) 167 { 168 if (refcount_sub_and_test(nr, &t->usage)) 169 __put_task_struct(t); 170 } 171 172 void put_task_struct_rcu_user(struct task_struct *task); 173 174 /* Free all architecture-specific resources held by a thread. */ 175 void release_thread(struct task_struct *dead_task); 176 177 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 178 extern int arch_task_struct_size __read_mostly; 179 #else 180 # define arch_task_struct_size (sizeof(struct task_struct)) 181 #endif 182 183 #ifndef CONFIG_HAVE_ARCH_THREAD_STRUCT_WHITELIST 184 /* 185 * If an architecture has not declared a thread_struct whitelist we 186 * must assume something there may need to be copied to userspace. 187 */ 188 static inline void arch_thread_struct_whitelist(unsigned long *offset, 189 unsigned long *size) 190 { 191 *offset = 0; 192 /* Handle dynamically sized thread_struct. */ 193 *size = arch_task_struct_size - offsetof(struct task_struct, thread); 194 } 195 #endif 196 197 #ifdef CONFIG_VMAP_STACK 198 static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t) 199 { 200 return t->stack_vm_area; 201 } 202 #else 203 static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t) 204 { 205 return NULL; 206 } 207 #endif 208 209 /* 210 * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring 211 * subscriptions and synchronises with wait4(). Also used in procfs. Also 212 * pins the final release of task.io_context. Also protects ->cpuset and 213 * ->cgroup.subsys[]. And ->vfork_done. And ->sysvshm.shm_clist. 214 * 215 * Nests both inside and outside of read_lock(&tasklist_lock). 216 * It must not be nested with write_lock_irq(&tasklist_lock), 217 * neither inside nor outside. 218 */ 219 static inline void task_lock(struct task_struct *p) 220 { 221 spin_lock(&p->alloc_lock); 222 } 223 224 static inline void task_unlock(struct task_struct *p) 225 { 226 spin_unlock(&p->alloc_lock); 227 } 228 229 #endif /* _LINUX_SCHED_TASK_H */ 230